For most of its 38 years, Elliott Management has been a lucrative hedge fund run solely by its founder, the billionaire Paul E. Singer, a man known for his hard-nosed trades and outsize influence in politics. Now for the first time, Mr. Singer will run the $27 billion investment firm with a partner who first joined 26 years ago by answering an employment ad in The Wall Street Journal. Elliott told its staff of more than 350 employees on Monday that it had appointed as co-chief executive Jonathan Pollock, who will help to steer the hedge fund as it continues...